The present invention is directed to an agriculture actives delivery composition comprising boron or persulfate ion-crosslinked polyvinyl alcohol microcapsules and a method of use thereof.
Microcapsules have been known for many years and have many and varied uses. For instance, microcapsules have utility in the areas of carbonless paper, pressure sensitive adhesives, pressure sensitive indicators, and fragrance delivery compositions.
Many processes for microencapsulation are known. These include methods for capsule formation such as described in U.S. Pat. Nos. 2,730,456, 2,800,457; and 2,800,458. Other useful methods for microcapsule manufacture are include those described in U.S. Pat. Nos. 4,001,140; 4,081,376 and 4,089,802 describing a reaction between urea and formaldehyde; U.S. Pat. No. 4,100,103 describing reaction between melamine and formaldehyde; and British Patent No. 2,062,570 describing a process for producing microcapsules having walls produced by polymerization of melamine and formaldehyde in the presence of a styrenesulfonic acid. Microencapsulation is also taught in U.S. Pat. Nos. 2,730,457 and 4,197,346. Processes for forming microcapsules from urea-formaldehyde resin and/or melamine formaldehyde resin are disclosed in U.S. Pat. Nos. 4,001,140, 4,081,376; 4,089,802; 4,100,103; 4,105,823; 4,444,699. Alkyl acrylate-acrylic acid copolymer capsules are taught in U.S. Pat. No. 4,552,811.
Common microencapsulation processes can be viewed as a series of steps. First, the core material which is to be encapsulated is emulsified or dispersed in a suitable dispersion medium. This medium is preferably aqueous but involves the formation of a polymer rich phase. Frequently, this medium is a solution of the intended capsule wall material. The wall material is thereby contained in the liquid phase which is also dispersed in the same medium as the intended capsule core material. The liquid wall material phase deposits itself as a continuous coating about the dispersed droplets of the internal phase or capsule core material. The wall material is then solidified. This process is commonly known as coacervation.
Phase separation processes, or coacervation processes are described in U.S. Pat. Nos. 2,800,457 and 2,800,458. Encapsulations based on polymerization of urea and formaldehyde, monomeric or low molecular weight polymers of dimethylol urea or methylated dimethylol urea, melamine and formaldehyde, methylated melamine formaldehyde, monomeric or low molecular weight polymers of methylol melamine or methylated methylol melamine, are taught in U.S. Pat. No. 4,552,811. These materials are typically dispersed in an aqueous vehicle and the reaction is conducted in the presence of acrylic acid-alkyl acrylate copolymers.
Polyvinyl alcohol microcapsules are taught by U.S. Pat. Nos. 3,886,084; 4,244,836; 4,269,729; 4,898,781; 5,064,650; 5,225,117; and 5,246,603.
In addition, core-material microcapsules have been used for many years in a variety of compositions, including but not limited to cleaning compositions. Perfume-containing microcapsules have also been used for many years in compositions designed to counteract malodors. Such microcapsules may contain a variety of cleaning solution-compatible components, such as cleaning oils, fragrances, colorants, etc. For instance, when used in hard surface cleaners such as floor cleaners, such microcapsules typically are intended to be subjected to crushing or disintegrating force upon application to a substrate to permit release of the core material, such as a fragrant oil.
Delivery systems for agricultural actives typically cannot rely on crushing or pressure or physical force methods in many fields of use. For example, an agriculture active dispersed on a leaf structure requires preferably a mechanism other than crushing for release of core material.
A disadvantage with respect to the use of prior art microcapsules produced by the above methods in, for example, the imparting of a fragrance during the cleaning of hard surfaces is that the microcapsules are somewhat resistant to rupture. As a result, the deposition of such microcapsules (which include a fragrant core material) is less than effective, as the microcapsules do not rupture absent physical force being applied. The microcapsules can also migrate into the pores of any porous surfaces to which the cleaning product is applied so as to further resist rupture.
Similarly agriculture actives deposited on a surface in microcapsules can be less than effective if the agriculture active is not available at the time when it can be most effective. Availability can be hindered if release is too slow or the microcapsules do not release the core contents absent physical force being applied.
U.S. Pat. No. 5,064,650 discloses salt-sensitive microcapsules. U.S. Pat. No. 5,364,634 discloses pH sensitive microcapsules. U.S. patent publication 2004/0115091 discloses perfume-containing microcapsules which are ruptured by the application of physical force.
It is thus desirable to provide a method for the formation of microcapsules which are susceptible to rupture or disintegration in the absence of applied force under the desired conditions of use.
It is further desirable to provide an aqueous delivery composition for agriculture actives containing microcapsules that can be used with advantage wherein microcapsules contained therein are susceptible to rupture or disintegration in the absence of applied force under the desired conditions of use.
It is further desirable to provide a method of crop field application or agriculture active delivery comprising the use of a solution containing the agriculture actives containing microcapsules of the present invention which are susceptible to rupture or disintegration in the absence of applied force under the desired conditions of use.